nix/doc/manual/glossary.xml
2005-04-01 15:34:23 +00:00

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<appendix><title>Glossary</title>
<glosslist>
<glossentry><glossterm>derivation</glossterm>
<glossdef><para>A description of a build action. The result of a
derivation is a store object.</para></glossdef>
</glossentry>
<glossentry><glossterm>store</glossterm>
<glossdef><para>The location in the file system where store objects
live. Typically <filename>/nix/store</filename>.</para></glossdef>
</glossentry>
<glossentry><glossterm>store path</glossterm>
<glossdef><para>The location in the file system of a store object,
i.e., an immediate child of the Nix store
directory.</para></glossdef>
</glossentry>
<glossentry><glossterm>store object</glossterm>
<glossdef><para>A file that is an immediate child of the Nix store
directory. These can be regular files, but also entire directory
trees. Store objects can be sources (objects copied from outside of
the store), derivation outputs (objects produced by running a build
action), or derivations (files describing a build
action).</para></glossdef>
</glossentry>
<glossentry><glossterm>substitute</glossterm>
<glossdef><para>A substitute is a command invocation stored in the
Nix database that describes how to build a store object, bypassing
normal the build mechanism (i.e., derivations). Typically, the
substitute builds the store object by downloading a pre-built
version of the store object from some server.</para></glossdef>
</glossentry>
<glossentry><glossterm>purity</glossterm>
<glossdef><para>The assumption that equal Nix derivations when run
always produce the same output. This cannot be guaranteed in
general (e.g., a builder can rely on external inputs such as the
network or the system time) but the Nix model assumes
it.</para></glossdef>
</glossentry>
<glossentry><glossterm>Nix expression</glossterm>
<glossdef><para>A high-level description of software components and
compositions thereof. Deploying software using Nix entails writing
Nix expressions for your components. Nix expressions are translated
to derivations that are stored in the Nix store. These derivations
can then be built.</para></glossdef>
</glossentry>
</glosslist>
</appendix>